The invention relates to an arrangement for detecting deficient operational capability of vacuum switching vessels which causes a signal to be given and/or causes a protective device to respond if a fault occurs.
The known vacuum switching vessels always require for proper operation a vacuum in the range of 10.sup..sup.-4 to 10.sup..sup.-7 Torr. If the vacuum becomes worse for any reason, the vacuum vessel can no longer interrupt the currents for which it is constructed. Then, the danger exists that an arc remains between the open contacts which damages or destroys the switching vessel and possibly also the switchgear in which the switching vessel is installed.
Damage of this kind can in principle be avoided by monitoring physical quantity determinative of the operational capability, namely, the vacuum. For instance, a signal could be given if the vacuum falls below a minimum value, or a protective device, for example, the tripping of a series-connected automatic protective circuit breaker could be made to respond simultaneously with the giving of a signal. Although the technical means are available for determining the vacuum and for evaluating the measured values, such means cannot be utilized in practice because the effort required and the cost is too high.
It is already known for monitoring the vacuum to provide a mechanical device which consists of an additional bellows-like part which is idle if the vacuum is correct, but executes a movement if the vacuum is diminished; this movement can be used to deliver a signal or to initiate protective measures. The bellows-like part, however, makes necessary a relatively complicated change in the construction of the switching vessel. In this connection, reference may be had to Deutsche Offenlegungsschrift 2,014,739.
Accordingly, it is an object of the invention to provide a detection arrangement which utilizes the principle of temperature dependence and affords the advantage of a simple evaluation as well as requiring only minor changes to the vacuum vessel itself.